TECHNIQUE OF DEVELOPMENT 



369 



Solution A is usually made by taking 750 cc. (3 qt.) of warm water and dissolving 

 the chemicals therein in the order given, then bringing to the volume indicated by the 

 addition of cold water. Care must be exercised in making solution B, which should be 

 mixed using cold water, as the solution of the hydroxide generates heat. For use, 

 take equal volumes of the two solutions, and mix them just before use. The develop- 

 ing time is usually about 2 min. at 65°F. 



Lithe Developers. — The maximum contrast requirements are encountered in 

 lithographic work where it is necessary to secure the maximum contrast between 

 exposed and unexposed areas. This is necessary both for line and half-tone work. 

 Special emulsions, formulas, and procedures are used to meet these needs, and some 

 of the developing formulas used are quite different than those encountered elsewhere 

 in photographic work. Both single-solution formulas and those mixed as two stock 

 solutions are recommended. 



Number 14 is indicated as more active than No. 15. Development is expected to 

 take about 1 min. at 70°F. for the former and toward 2J2 rnin. with the latter. The 

 lower dilutions indicated under the "range" heading may be expected to produce less 

 density. 



One basic formula is recommended for preparation as two-stock solutions. Two 

 different manufacturers recommend essentially the same formulas except that one 

 suggests the addition of 20 cc. of phenosafranine solution (1:1000) to solution A. 



No. 16 Paraformaldehyde Developer 



Solution A 



Sodium sulphite (anhydrous) 1 . g. 58 gr. 



Paraformaldehyde 30.0 g. 4 oz. 



Potassium metabisulphite 10 . 5 g. 1 oz. 175 gr. 



Water to 1 1. 1 gal. 



Solution B 



Sodium sulphite (anhydrous) 120 g. 1 lb. 



Boric acid (crystals) 30 g. 



Hydroquinone 90 g. 12 oz. 



Potassium bromide 6 g. 350 gr. 



Water to 3 1. 3 gal. 



For use, mix one part of solution A and three parts of solution B. Development 

 times oi \]/2 to 3 min. may be expected at 65 to 70°F. 



